Method of shoeing permanent magnets.



A. D. PENTZ.

METHOD OF SHOEING PERMANENT MAGNETS.

APPLICATION FILED SEPT- 5.1914.

Patented July 1916.

2 SHEETSSHEET I.

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AID. PENTZ.

METHOD OF SHOEING PERMANENT MAGNETS.

APPLICATION FILED SEPT. 5,19I4- I Patented July 25, 1916.

2 SHEETS-SHEET 2.

His Attorney Inventor xlbert D. Peniz,

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ALBERT 1D. PENTZ, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

METHOD OIE SHOEING PERMANENT MAGNETS.

- permanent magnets, and in particular a novel and improved method ofshoeing the permanent damping magnets of electric mo- .tor meters.

More specifically, the object of my invention is to provide a simple,convenient, inexpensive, and positive method of securing an attachingshoe to the permanent magnets of an electric motor meter.

Considerable difiiculty has heretofore been experienced insatisfactorily securing an at taching shoe to the damping magnets of anelectric meter. As is well understood in the art, the manner ofattaching the shoe to the magnet must not aifect the magneticcharacteristics and properties of the magnet, and,

since the magnet is of hardened steel, the

ways in which a shoe may be securely and satisfactorily attached theretowithout injuring the magnetic properties of the magnet are limited.Heretofore, it has been generally customary to provide the shoe withlongtoes which are bent about the magnet so as to firmly clasp the same.The toes are manually hammered around the mate rial of the magnet, and,first on account of the peculiar configuration of a meter magnet, butmore on account of the inherent nature of a hammer blow as hereinaftereX- plained, a secure engagement of the toes of the shoe with the magnetis diflicult, and consequently the magnet frequently becomes loose inthe shoe. Furthermore, it has heretofore been the practice to bend thetoes of the shoe about the magnet by hand. in order to obtain results inany degree satisfactory, and this operation is objectionably expensive.

I have devised a novel and improved method. of shoeing a permanentmagnet whereby the shoe is firmly and positively secured to the magnet,so that even after un- Specification of Letters Patent.

Patented July 25, 1916.

Application filed September 5, 1914;. Serial No. 860,349.

usually rough treatment the magnet is firmly held to the attaching shoe.I have also devised a simple, novel and economic type of shoe whichserves to hold a permanent magnet of special sectional configurationsecurely fastened thereto. The method of shoeing and the form of themagnet and shoe are further of such a character that the shoe can bereadily applied to the magnet by mechanical means at a nominal cost.

The novel features of my present inyention which I believe to bepatentable are definitely indicated in the claim appended hereto.

My improved method of shoeing a permanent magnet and the advantages andnovel character of the same will be understood from the followingdescription taken in connection with theaccompanying drawings, in which:

Figure 1 is a partial perspective view of a machine designed to carryout my novel method of shoeing a permanent magnet; Fig. 2 is a sectionalview taken on the line 22 of Fig. 1 showing a detail of the ma chine andillustrating the means for forcing the shoe under pressure into intimatecontact with the magnet; Fig. 3 is a view of a ,pair of meter magnetssecured to an attaching shoe in accordance with the principle of myinvention; Fig. 4 is a partial sectional view on line 4-4 Fig. 3, of oneof the magnets and the shoe shown in Fig. 3; Fig. 5 is a view of a pairof meter magnets of modified design secured to an attaching shoe inaccordance with the principle of my invention; Fig. 6 is a view of oneof the magnets shown in Fig. 5; Fig: 7 is a section on the line 77 ofFig. 5 before the shoe has been forced under pressure into its clampingposition; Fig. 8 is a section on the line 7-'( after the shoe has beenforced under pressure into its clamping position; and Fig. 9 is a'detailexplanatory View. Heretofore, it has been generally customary to make ameter magnet with rounded edges, as indicated in dotted lines in Fig. 9of the accompanying drawings. The attaching shoe for such a magnet isprovided with long toes which are manually hammered over the-roundededges of the magnet. In

accordance with my present invention, the

magnet is given a substantially trapezoidal section, as shown in Figs.4, 7, 8 and 9 of the drawings. This peculiar sectional configuration ofthe magnet lends itself to a very simple andv most effective method ofshoeing. The shoe, in accordancewith my invention, has short relativelyheavy lugs instead of the former long relatively thin toes, and theselugsfare squeezed under a considerable stress, for example in theneighborhood of twenty tons, into intimate contact with the magnet.

As before stated, the toes of the attaching shoe have heretofore beenhammered about the magnet. A hammer blow is sudden and always permitsthe hammered metal to rebound. Hence, it is extremely difiicult, if notimpossible, to effect an intimate and secure engagement between the shoeand magnet by a hammering action. A squeeze differs materially from ahammer blow, particularly in that with a squeeze there is an instant ofrest under compression during which the metal substantially flows intothe condition under which it exists when compressed, so that after thepressure is removed the molecules of the metal have readjustedthemselves to the compressed condition, and there is consequently littleor no tendency to rebound.

My novel and improved method of shoeing a permanent magnet thus consistsin squeezing the shoe onto the magnet with a pressure of several tons tothe square inch, and maintaining the state of compression between theshoe and the magnet, occasioned by such squeezing action, for anappreciable length of time, and until the metals ,of the shoe and magnethave adjusted themselves to the new molecular conditions occasioned bythe squeeze.

Reference to the accompanying drawings will explain more clearly my.present invention.

Fig. 3 illustrates a pair of permanent magnets 10 secured. to a shoe 11in accordance with the principle of my invention. The permanent magnets10 are of a well known design employed in electric, motor meters fordamping the rotation of the movable element. The magnets are adapted tobe securely fastened to the shoe 11 in accordance with the principle ofmy invention, and are then suitably mounted in the meter by means of thescrew-threaded holes 16 in the shoe, in such a manner that the dampingdisk of the meter is operatively positioned in the air gaps of themagnets in the Well known way.

The shoe 11 is cast of composition metal,

which, as is Well known, is considerably softer than the hardened steelof the magnets. In accordance -with-my present invention that portion ofeach permanent magnet to which the shoe is attached is of substantiallytrapezoidal cross-section. This will be clearly seen by reference toFig. 4 of the drawings,.wherein the magnet 10 is moaeao represented ashaving a substantially quadrilateral cross-section with two sidessubstantially parallel and the other two sides nonparallel andconverging toward each other. The shoe has a base portion 12 which isadj acent the longer of the two parallel sides of the magnet and whichis provided with projections 13 in engagement with this side of themagnet. It will be observed that the projections 13 are the only partof-the base portion 12 of the shoe in actual contact with the magnet andthat the remainder of the base portion extends substantially parallel tothe longer of the two parallel sides of the magnet, but is separatedtherefrom by a narrow air space. The shoeis cast of composition metal,and is secured to the magnet in its ca'st condition without any previousmachining. Since it is substantially impracticable to cast the shoe sothat the base portion 12 has a perfect plane surface, it is necessary toprovide the projections 13, which form four points of support for eachmagnet and serve to satisfactorily position the magnet with respect tothe shoe, regardless of any irregularities upon the adjacent surfaces ofthese two members. The base portion 12 of the shoe is provided with acentral boss 14 which determines the minimum distance between the twomagnets 10 as will be clearly seen in Fig. 3 of the drawmgs.

The shoe 11 has integrally attached thereto twopairs of lugs 15, eachpair of lugs being adapted to firmly secure one of the permanent magnets10 to the shoe in accordance withthe principle of, my present invention.It will be observed that the lugs 15 are designed to engage with the twononparallel sides of the magnet.

In shoeing the magnet in accordance with my novel and improved method,the magnet is first placed in its proper position with respect to theshoe. The magnet and shoe, thus assembled, are placed in a power press,such for example as is represented in Figs. 1 and 2 of the drawings, andthe press is then operated to squeeze or force the lugs 15 into veryintimate contact with the non-parallel sides of the magnet under apressure of several tons to the square inch.

The press shown in Figs. 1 and 2 has a central alining member 20, whichis adapted to extend through the air gap between the poles of each ofthe two magnets 10, and which serves as a centering axis for the magnetsand the shoe. The alining member 20 is mounted upon a rockable plate 29,which latter also carries the lower die 27 of the press. The plate 29also has secured thereto three posts 31 and 32. The post 32 is adaptedto enter the space between the ends of the assembled magnets and servesto properly and accurately determine the ill) incense supporting member.A hand operated lever 21 has a fined pivot 19, and is connected bylinkage to to the slidable base 34. A wedge 17 is mounted on the linkagel8, and is adapted to he forced loy movement of the lever 21 against ablock 22 bolted to the lbase 34. Movement of the lever thus operates tomove the hase 3a, through the engagement of the wedge 17 with the 'bloch22,

thereby carrying the plate 29' and the as sembled magnets'and shoetoward astation- The stationary block 24 has. wear plates 33 which areadjacent the heels ary block 2st.

of the shoe .11. When the .slidahle base is moved towardv the loloclr 2dthe assemhled magnets and shoe are firmly and accurately secured betweenthe posts 31 and the wear plates 33, and are thus ready for the saucesing operation.

. The part oi the press alcove described, called the lirture, issuitably supported by a base member and springs of great rigidity totalre up the shoclr of and to cushion the great pressure to which thetin ture is subjected during the squeezing" open ation.

Since the construction or power press :lornis no pzurlwai my presentinvention, l have merely indicated in Figs. it and 2 only thoseessential elements oi? the construction necessary for a clearunderstanding oi my novel method or shoeing a permanent net.

hen magnets and shoe are properly press firmly held hepositioned in thetween the posts 31- the wear plates 33,

a vertical 'olun er 25 earn ins the umer ,L if; a) 4 die is "forced downupon the shoe, and the lugs l5 are squeezed into intimate contact withthe magnets between the upper die 26 and the lower die 27', as will hehest understood by reference to -Eiir. 2 of the drawings. pressureapplied during this squeezing operation is in the neighloor hood oi 2Utons and the metal of the shoe is virtually crushed into very intimatee1 gagement with that oil the magnets. The are maintained in a statecompression occasioned lay the squashing action tor appreciahle lengthoi time, for example, one, two orrnore seconds, and until the metals ofthe shoe and magnets have had sulficient time to: prevent material.rehound oi the metal oi the shoe alter the pressure has heen removed.

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The entire operation is carried on under normal temperature conditions,that 18 at ordinary room temperature, and the squeezing of the lugs ofthe shoe into intimate contact with the magnet is efi'ected by pressurealone, and without the application of airy heat for softening the metalof the s oe. 1

The manner in which the in s 15 engage the trapezoidal cross-section othe permanent magnets will be evident from an inspection of Fig. 4: oi?the drawings. It will be observed from Fig. 3 of the drawings that thecentral boss it acts to prevent lateral movement of the magnets towardone another and that the elbow 17 of each magnot, which is held firmlyclamped between the lugs 15, prevents movement of the magnets away fromone another. lln magnets which have not a curved elbow hire the magnetsshown in Fig. 3, l have found it advisable to impart an irregularity tothe surface of the magnet to prevent any tendency of relative lateralmovement between the shoe and magnet. This feature oi? my invention willbe understood loy reference to Figs. 5, 6, l and 8 of the accompanyingdrawings. in these figures two magnets are shown secured to a shoe 36 inaccordance with the principle or any invention. The lugs 3i oi? the shoeare forced into intimate contact with the non-parallel sides oil themagnet in exactly the same manner as heretoiore de scribed. Each magnethas an irregularity or indentation 39 on its surface. When the lugs areforced under pressure into contact with the sides oi the magnet, themetal of the lugs is forced into the irregularities 39, whereby relativelateral movement of the shoe and magnet is prevented.

din-cc the metal or" the shoe is consid erably softer than that oi themagnet, former will he forced to conform to the configuration of thelatter, so that loy the powerful squeezing action to which the assembledshoe and magnets are subjected the metal of the shoe will he liter allyforced into any depressions 111 the surface of the magnets. Theirregularity the surface oi the magnet is hence preferably in the natureof a notch which can he cut or struck "in the magnet in any suitable wayand into which the metal of the shoe is forced by the squeezing action.

will cit course he understood that more than one irregularity may heimparted to the surface or the magnet, the important condition to hefulfilled being that the ir regularity, or irregularities, he oil such acharacter the metal of shoe forced into theirregularity to preventpossilole relative lateral movement of the magnet with respect to theshoe. o

The shoe 3% is provided with a progection in the nature of a ridge 38,similar in limeldll - ners indicated by reference letter i).

tion to the projections 13, so that the ridge is the only part of thesurface of the base portion of the shoe 36 in actual contact with themagnet. Screw-threaded holes l0 and 41 serve to mount the shoe andattached magnets in the meter.

The trapezoidal section which I give the permanent magnets in carryingout my invention results in a substantial saving in the materialof themagnet for the same efiective damping. For example, consider the twotypes of magnets illustrated in Fig. 9 of the drawing. The effectivedamping zone of the rounded-edge magnet, partially represented in dottedlines, is indicated by the line A. The effective damping zone of themagnet of trapezoidal section, shown in full lines, is indicated'by thesame line A. The rounded-edge magnet and the magnet of trapezoidalsect-ion thus produce the same effective damping and the saving inmaterial effected by the application of my invention amountssubstantially to the area of the cor-- The areas a must obviously besubtracted from the areas 7) to accurately determine the actual savingin material, but it will be evident that the area a is very considerablysmaller than the area I), and hence that the saving in the material ofthe magnet is very substa ntial Tt will be evident from the foregoingdescription and explanation that I have provided a simple and'effectivemethod of shoeing a permanent magnet. By the application of my inventiona very considerable economy is also effected in the amount of materialrequired for the shoe, since the amount of material in a shoe designedin accordance with the principle of my invention is considerably smallerthan in a shoe with long toes, such as heretofore generally employed.members as the toes of the former shoes are bent about a magnet to clampthe same, the degree of bending, that is the angle through which a toeis bent, is very large, and the shoe must be made of a relatively highgrade of alloy to withstand such excessive bending. In the case of mymethod of shoeing and novel construction of shoe the attaching lugs areshort, and the degree of bending is relatively small, so that a muchlower grade of alloy may be employed for the shoe.

What I claim as new and desire to secure by Letters Patent of theUnited'States, is

The method of securing a shoe having eX- tending lugs to a permanentmagnet which consists in'squeezing the lugs of the shoe under normal.temperature conditions onto the magnet with a pressure sufficient tovirtually crush the lugs of the shoe into intimate contact with themagnet, and maintaining the state of stress between the lugs of the shoeand the magnet occasioned by such squeezing action for a length of timesufficient to prevent material reboundof the lugs from the magnet afterthe pressure has been removed.

In witness whereof, Thave hereunto set my hand this 2nd day ofSeptember, 1914.

ALBERT D. PENTZ. Witnesses:

JOHN A. MCMANUS, -Jr., JOHN T. -BEEOHLYN.

Furthermore, where such long,

